Torque-journal hub propeller



Oct 7, 1969 5, SIATTERTHWMTE ETAL 7 3,470,843

TORQUE-JOURNAL HUB PROPELLER Filed July 7, 1956 2 Sheets-Sheet 1.

FIG.- I Y 7 4s ll 2 I9 42 I4 |6C-/ 26 2B 29[ 8 INVENTORS.

J. GLENN SATTERTHWAITE JAMES B. MACY JR.

ATTORNEYS McNENNEY, FARRINGTON, PEARNE Bu GORDON 1969 J. G.SATTERTHWAITE ETAL 3.470,843

TORQUE-JOURNAL HUB PROPELLER 2 Sheets-Shea. j

Filed July 7, 1966 YINVENTORS. J. GLENN SATTERTHWAITE JAMES B. MACY JR.

Mc NENNY, FARRINGTON,PEARNE 8 GORDON ATTORNEYS United States Patent3,470,843 TORQUE-JOURNAL HUB PROPELLER James Glenn Satterthwaite, 1Dogwood Trail, Chesapeake, Va. 23321, and James B. Macy, 107 Holly Lane,Morehead City, N.C. 28557 Filed July 7, 1966, Ser. No. 563,516 Int. Cl.B63h 5/06, 1/14; F16c 33/22 US. Cl. 115-34 20 Claims ABSTRACT OF THEDISCLOSURE A marine propeller assembly has a cylindrical hub with aplurality of blades secured directly thereto. The hub is relativelylarge, extends through the hull and is provided with an integralextension inside the hull. The extension has a connecting means which isat least as small as the inner radius of the bearing for the hub.

This invention relates generally to marine propulsion systems and moreparticularly to a novel and improved marine propeller assembly.

Conventional marine propulsion systems include a solid steel tail shaftwhich supports a propeller at its rearward end and extends forwardthrough a stern bearing to the rearward end of the ships line shafting,The tail shaft is usually sized to fit into the propeller hub, andmating tapers and keys are used to transmit the propulsion torque fromwithin the propeller hub.

With such prior art systems, including a propeller tail shaft, severefatigue, fretting and corrosion problems are encountered due toinsufficient rigidity. These problems occur where the propeller ismounted on the shaft and in sleeved areas Within the bearing zone.

In propulsion systems utilizing steel tail shafting a liner or sleeve ofcorrosion resistant material, such as bronze, must be mounted on theportion of the propeller shaft within the bearing. This sleeve causesstress concentrations, principally at its ends, which produce fatigue,fretting and corrosion. Oil lubricated bearings are sometimes used,however, such oil lubricated bearings are compli cated, expensive andrequire a high degree of maintenance.

A comprehensive discussion of these and other problems is contained in apublication of the United States Department of Commerce, MaritimeAdministration, entitled Design Improvements and Standardization ofPropulsion Shafting and Bearings by Sterling A. Fielding, Division ofShip Design, Ofiice of Ship Constructions, Maritime Administration. Itis believed that this publication was presented as a paper to theChesapeake Section of the Society of Naval Architects and MarineEngineers on Nov. 17, 1965.

In one of its broader aspects this invention provides a novel andimproved propeller and propeller bearing structure which eliminates thepropeller tail shaft along with its fatigue, corrosion and frettingproblems.

The present invention also eliminates one of the principal problemswhich has limited the use of water lubricated rubber bearings,particularly on larger ships. It has been found that water fails toprovide adequate lubrication for rubber bearings when the surfacevelocity of the journal is below twenty-five feet per minute.

In many ships, particularly those provided with turbine power, it isnecessary to rotate the engines and propeller at a slow speed while theship is in port, to provide even cooling of the power plant turbineblades. This is normally referred to as jacking. Since the thrustproduced by the propeller and the power required for jacking are bothdirect functions of jacking speed, jacking is performed at a speed asslow as possible. In very large ships the jacking speed is usually about3 to 4 r.p.m. and in smaller ships the jacking speed is about 10 r.p.m.

When conventional propeller shafts are used, such jacking often resultsin journal surface velocities within a rubber bearing which are Wellbelow twenty-five feet per minute. Consequently, jacking often resultsin damage of the rubber bearing material by roughing the surface andrendering it useless for adequate lubricating at normal operatmg r.p.m.

In another of its broader aspects, this invention provides a sternbearing structure wherein the diameter of the journal is sufficientlylarge to provide surface velocities having a magnitude suflicientlygreat to maintain proper water lubrication of a rubber bearing evenunder jacking conditions. Such a journal with its large diameterprovides greater area for a given length and results in lower bearingpressures. This decreases wear and provides greater system stability.Also, in a given installation it permits the use of a shorter bearingwhile maintaining bearing loading within acceptable limits. Stillfurther, it results in more eificient operation, since the friction of awater lubricated rubber bearing tends to drop as the journal velocitywithin the bearin is increased.

In one propeller structure incorporating this invention a one piecepropeller is formed with an elongated or tubular hub which extendsthrough the stern tube bearing within which it is fully journaled and isconnected directly to the ships internal shafting, thus absorbing thefull torque of the shafting system. The hub, like the propeller blades,is formed of a corrosion resistant material, such as stainless steel orbronze, so it is not necessary to provide a noncorrosive liner orsleeve. Consequently, fretting and fatigue in the bearing area areeliminated. Because of the relatively large outside diameter of thehollow hub it has an increased section modulus and suflicient strengthis provided without excessive Weight even when the hub is formed of anon-ferrous material, such as bronze. The coupling of the propeller andthe internal shafting is easily accomplished since the large diameter ofthe extended hub provides a sufficient large radius to permit the use ofa bolt circle type coupling between the propeller hub and the internalshafting.

In aonther embodiment of this invention removable blades are mounted onthe tubular hub. The tubular hub provides a central opening whichprovides internal access to simplified internal fastening means whichsecure the blades on the hub.

It is an important object of this invention to provide a novel andimproved marine propulsion system constructed and arranged to minimizefatigue, corrosion and fretting.

It is another important object of this invention to provide a novel andimproved marine propulsion system wherein the hub which supports thepropeller blades extends through and is entirely laterally supported bythe stern bearing.

It is another important object of this invention to provide a propulsionsystem, according to the last preceding object, wherein the sternbearing is rubber and the hub is provided with a sufficiently largediameter to produce adequate water lubrication of the bearing even atjacking speeds.

It is another important object of this invention to provide a novel andimproved propulsion system, according to any of the precedingobjects,wherein the propeller hub is directly connected to the shipsinternal shafting on the forward side of the bearing remote from thepropeller blades.

It is still another object of this invention to provide a novel andimproved propeller structure for marine propulsion having removableblades.

Further objects and advantages will appear from th following descriptionand drawings wherein:

FIGURE 1 is a fragmentary side elevation, partially in section,illustrating one embodiment of a propeller and stem bearing structureincorporating this invention;

FIGURE 2 is an enlarged fragmentary section of the embodimentillustrated in FIGURE 1;

FIGURE 3 is a fragmentary end view of the structure illustrated inFIGURE 2 with the bearing stave retaining plate removed;

FIGURE 4 is a fragmentary side elevation of a second embodiment of thisinvention illustrating a propeller with removable blades and a modifiedform of the coupling between the propeller hub and the ships internalshaft- FIGURE 5 is an enlarged, fragmentary section illustrating thestructural detail of one form of mounting the blades on a propeller hub;and

FIGURE 6 is an enlarged, fragmentary section illustrating the structuraldetail of another embodiment for mounting the blade on the propellerhub.

Referring to FIGURES 1 through 3, the stern portion, schematicallyillustrated at 10, of the ships hull is provided with a cylindricalopening 11 sized to receive rubber staves 12 of a water lubricatedrubber bearing assembly 13. A stufiing box assembly 14 is bolted on theforward side of the opening 11. The assembly 14 provides a radiallyextending surface against which one end of each of the staves 12 abuts.Mounted adjacent to the other end of the cylindrical opening 11 is aheavy duty segmented ring 16 removably secured in place by bolts 17. Thevarious elements are proportioned so that the ring 16 cooperates withthe assembly 14 to provide axial compression of the bearing staves 12 tosecure the bearing staves in position by radial expansion. Reference maybe made to our co-pending application, Ser. No. 515,395, filed Dec. 21,1965, for a more complete description of this and other structures forremovably mounting rubber bearing staves in a water lubricated rubberbearing structure.

A one piece propeller 18 is provided with a hollow hub 19 from one endof which extends a plurality of integrally formed propeller blades 21.The hub portion 19 is faired at its rearward end 22 and its forwardportion extends through the bearing 13, past the stuffing box assembly14 to the interior of the ships hull. The illustrated stuffing boxassembly 14 is provided with seals 16C which are compressed by a ring16a and tension bolts 16b. The stufiing box assembly 14 can be movedforward along the shafting to permit inboard removal and replacement ofstaves.

The hub portion 19 has an axially extending central opening 26 whichextends with substantially uniform diameter from a closed end at 27 to asubstantially conical inner face 28 joining the main opening 26 with areduced diameter forward opening 29. Adjacent to the forward end of thehub 19, forward of the conical surface 28, is an annular groove 31defining the rearward side of a mounting flange 32. Extending inwardfrom the periphery of the forward side of the flange 32 is a radial face33 adapted to fit against a mating end face 34 of a flange 39 on theships internal shafting 36. In the illustrated embodiment the end face33 is provided with an axial projection 37 around the opening 29 whichfits a mating recess 38 on the shafting 36 to assist in laterallylocking the joint. The flange 32 and flange 39 are formed with boltholes through which a plurality of bolts 41 extend. In this embodimentthe annular groove 31 provides access for the nuts 42 on the bolts 41.The adjacent end of the internal shafting 36 is supported for rotationabout its longitudinal axis by a bearing 43 secured to the stern portionof the hull.

This illustrated embodiment of this invention completely eliminates theconventional tail shaft and its corrosion resistant liner. Instead itprovides a large diameter, one piece tubular hub. The hub, because ofits large section modulus is capable of efficiently absorbing all of thetorsional and bending stresses encountered even when it is formed ofnon-ferrous metal. It does not provide objectionable points of stressconcentration, so fatigue problems are virtually eliminated. Also, theuse of a one piece, non-corrosive hub eliminates fretting and corrosionproblems. In most installations the total weight of the propeller is nogreater than the weight of a conventional propeller with its tail shaftassembly.

Also, the diameter of the stern bearing is substantially increased dueto the larger journal diameter. Consequently, surface velocity of thejournal is substantially higher for a given r.p.m. For example, in theconventional prior art system utilizing a propeller shaft or tail shaft,a twenty-four foot diameter, five bladed propeller is normally mountedon a tail shaft having a diameter of about twenty-eight inches. Suchshafts are usually provided with a corrosion resistant liner of aboutone and one half inches in radial thickness. Consequently, the exteriorof the liner mating with the bearing has a diameter of about thirty-oneinches. Such a propeller usually has an outer hub diameter of about fivefeet. When operating at a jacking speed of three r.p.m. the surfacespeed of such a system would be less than twenty-five feet per minuteand roughing of the rubber bearing material surface is likely to occurdue to insufiicient lubrication.

An installation of the same size incorporating the present inventionwould provide an extension of the hub and elimination of both the tailshaft and liner. The outer surface of the hub mating with the bearingwould have a diameter of about five feet and at a jacking speed of threer.p.m. would provide a surface velocity in the bearing of aboutforty-seven feet per minute. Such a surface speed is well above thespeed required to maintain good water lubrication of the bearing andwear is substantially eliminated during jacking conditions.

Such a propeller would be operated under normal power conditions atbetween ninety and one-hundred and five r.p.m. and under such conditionswould provide bearing surface velocities between fourteen-hundred andsixteen-hundred and fifty feet per minute. On the other hand, with theprior art arrangement with an inner bearing diameter of about thirty-oneinches such shaft speeds would produce surface velocities of aboutseven-hundred and thirty to eight-hundred and fifty feet per minute. Inrubber bearings the friction of the bearing tends to decrease as thesurface velocity of the bearing increases. Consequently, the presentinvention with a larger bearing provides decreasing friction whencompared to conventional designs under all operating conditions.

The use of the present invention also results in improved structuralarrangements because the stern bearing can be shorter for a given sizepropeller without increasing the bearing pressure. In rubber bearings itis desirable to maintain the bearing pressure in the order of ten tofifteen pounds per square inch and always less than twenty-five poundsper square inch. With the present invention acceptable bearing pressuresare achieved generally when the bearing length is about one andonequarter times the hub diameter. Consequently, when the hub diameteris five feet the bearing length can be in the order of six andone-quarter feet. However, a rubber bearing for a twenty-four footpropeller described above utilizing conventional structures normallyrequire a hearing length of about ten feet. Consequently, with prior artarrangements it has been necessary to provide a ships hull with a longerbearing supporting structure. Preferably, the flange 32 has a diameterat least as small as the diameter of the hub 19, so that the propellercan easily be inserted through the bearing section. However, because theflange 32 is relatively large in diameter a simple bolt ring typecoupling provides sufficient strength to transmit the propulsion torquefrom the ships internal shafting 36 to the propeller.

Preferably, a slot 35 between the blades 21 is provided which issufiiciently wide to permit the axial removal and replacement of staves12 without removing the propeller. This arrangement is best illustratedin FIGURE 3. Reference should be made to our co-pending application,cited above, for a more detailed description of various structuralarrangements and methods for servicing stave type rubber bearings.

Because the hub of the propeller 19 is hollow, strain gauges or othertesting and measuring devices may be permanently aflixed within thepropeller to provide continuous indications of the conditions of thepropeller.

FIGURE 4 discloses another embodiment of this invention whereinremovable blades 51 are mounted within a tubular hub 52. Here again, thehub 52 is formed of corrosion resistant material, such as stainlesssteel or bronze, and extends with the uniform diameter through a rubberbearing 53 and seal assembly 54. In this embodiment the ships internalshafting 36 is provided with a flange 39 which fits against the forwardend 56 of the hub 52. The coupling is provided in this instance by studbolts 57 threaded into the forward end of the hub 52. Consequently, anannular groove is not provided on the forward end of the hub, asillustrated in FIGURES 1 through 3, and the internal bore 58 within thehub has a uniform diameter. A cap member 59 is removably bolted to therearward end of the hub 52 to provide access to the bore 58 for removaland replacement of the blades 51.

Referring to FIGURE 5, one structural arrangement for securing each ofthe blades 51 to the hub 52 includes a radially extending recess 61preferably having the shape of a truncated cone. A mating boss 62 formedon the inner end of the blade 51 fits into the associated recess. A stud63 threaded into the boss 62 extends through a radial opening 64 and isthreaded to receive a nut 66 within the central opening 58 of the hub52. A dowel pin 67 is eccentrically mounted with respect to the conicalopening 61 and extends into the hub 62 to insure that the blade 51 ismounted at the proper pitch angle. Preferably, the angle of the conicalopening 61 and the mating surface of the boss 62 is arranged to providea locking taper.

When a blade 51 must be removed the end member 59 is first removed toprovide access to the central opening 58. The nut 66 is then removed andjacking means are used to break the taper loose. A new blade can then beeasily installed and after the end member 59 is replaced the propelleris ready for subsequent use.

FIGURE 6 discloses still another structure for removably mounting theblades. In this embodiment the blade 71 is again provided with a boss 72formed with a conical outer surface mating with a conical recess 73 inthe hub 74. However, the hub is provided with a plurality of radiallyextending bolt holes 76, symmetrically arranged about the central axisof the recess 73, each receiving a stub bolt 77 threaded into the innerend of the boss 72. Preferably, the inner wall of the opening 58 isprovided with a flat boss portion 78 against which nuts 79 bear. In thisembodiment the pitch of the blades can be changed by an amount equal tothe angular spacing between adjacent stud receiving holes 76.

Here again, the hub 74 is provided with a removable end member foraccess purposes. Also, measuring devices such as strain gauges, or thelike, may be mounted within the hub of either removable bladeembodiment.

Although preferred embodiments of this invention are illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the invention.

We claim:

1. A marine propeller assembly adapted to be supported on the hull of avessel comprising an elongated cylindrical hub, a plurality of bladesdirectly connected to said hub substantially adjacent to its rearwardend, said hub being formed with an axial extension providing acylindrical external bearing surface axially on one side of said blades,a bearing adapted to be mounted on said hull, said bearing beingpositioned around said bearing surface to laterally support saidpropeller, said extension providing a portion substantially on the sideof said bearing remote from said blades provided with connecting meansadapted to releasably connect said hub with drive shafting so that thedrive torque applied to said propeller by such drive shafting istransmitted through said extension, the maximum radius of said portionof said extension and said connecting means being at least as small asthe inner radius of said bearing so that said propeller may be removedfrom said bearing by axially rearward movement thereof with respect tosaid bearing.

2. A propeller assembly as set forth in claim 1 wherein said hub istubular and is the principal structural element between said connectingmeans and said blades.

3. A propeller assembly as set forth in claim 1 wherein said hub has asubstantially uniform cross section from the location where said bladesare connected to a location substantially adjacent to said connectingmeans.

4. A propeller assembly as set forth in claim 2 wherein said connectingmeans includes a radially extending end face adapted to seat against amating surface on the line shafting of a ship and provided with a boltcircle to secure the hub to said line shafting.

5. A propeller assembly as set forth in claim 4 wherein said end face ison a flange formed with a plurality of bolt holes therethrough, saidbolt holes being radially spaced from the axis of said hub, said flangeproviding a rearward face adapted to be engaged by bolts when saidflange is clamped by such bolts to said mating surface.

'6. A propeller assembly as set forth in claim 5 wherein the maximumdiameter of said flange is no greater than the diameter of said bearingsurface, said hub being formed with an annular groove to provide therearward face of said flange, and the central opening in said hub havinga reduced diameter adjacent to said flange and groove.

7. A propeller assembly as set forth in claim 4 wherein a plurality ofaxially extending, threaded holes open through said end face, each holebeing adapted to receive a threaded fastener for securing said hub tothe line shafting of a ship.

8. A propeller assembly as set forth in claim 7 wherein said hub isformed with a substantially uniform cross section between said end faceand the location of said blades.

9. A propeller assembly as set forth in claim 2 wherein said hub isformed entirely of a corrosion resistant metal.

10. A propeller assembly as set forth in claim 9' wherein said hub andblades are integrally formed of said corrosion resistant metal.

11. A propeller assembly as set forth in claim 9 wherein said blades areremovably secured to said hub.

12. A propeller assembly as set forth in claim 11 wherein said hub isformed with a plurality of radially extending recesses, and each bladeis formed with a mounting boss at its inner end fitting into and matingwith an associated recess, and clamping means removably securing eachboss in its associated recess.

13. A propeller assembly as set forth in claim 12 wherein said recessesand bosses are truncated cones.

14. A propeller assembly as set forth in claim 13 wherein said clampingmeans includes threaded fastening means extending into and accessiblewithin the central opening of said hub.

15. A propeller assembly as set forth in claim 14 wherein said threadedfastening means extends along the axis of each boss and associatedrecess, and locating means are provided between said hub and boss at aposition radially spaced from said fastening means.

16. A propeller assembly as set forth in claim 14 wherein said fasteningmeans includes a plurality of threaded fasteners symmetrically locatedin a circle around the axis of each boss and its associated recess.

17. A propeller assembly as set forth in claim 14 wherein said hub isclosed at its rearward end by a removable end member, the removal ofsaid end member providing access to said threaded fastener means.

18. A marine propeller assembly as set forth in claim 1 wherein saidbearing is a water-lubricated rubber bearing having a length notsubstantially greater than oneand-one-quarter times its diameter, thesurface pressure of said hub on said bearing created by the weight ofsaid propeller being less than about 25 pounds per square inch, and sealmeans are provided engaging said portion of said extension between saidbearing and said connecting means.

19. A marine vessel comprising a hull having a stern, a propulsionsystem in said hull including shafting extending to a location adjacentto said stern, a propeller bearing mounted on said hull at said stern,and a propeller assembly journaled in said propeller bearing, saidpropeller assembly including an elongated cylindrical hub, a pluralityof blades directly connected to said hub outboard from said bearing,said hub being formed with an axial extension extending through saidbearing and providing a cylindrical external bearing surface axially onone side of said blades engaging said bearing and laterally supportingsaid propeller, said extension providing a portion substantially on theside of said bearing inboard thereof provided with connecting meansreleasably connecting said hub with said shafting so that drive torqueapplied to said propeller by said shafting is transmitted through saidextension, the maximum radius of said portion of said extension and saidconnecting means thereon being at least as small as the inner radius ofsaid bearing so that said propeller may be removed from said hull byrearward axial movement thereof without removing said bearing from saidhull.

20. A marine vessel as set forth in claim 19 wherein said propulsionsystem is periodically operated at jacking speeds, said bearing is awater-lubricated rubber bearing, and the surface of said bearingengaging said propeller is sufficiently large so that the surfacevelocity therebetween is at least 25 feet per minute when saidpropulsion system is rotating at jacking speeds.

References Cited UNITED STATES PATENTS 796,810 8/1905 Clarkson 1l534914,857 3/1909 Miller. 1,799,192 4/ 1931 Schallert. 2,664,961 1/1954Goede 170160.6 2,732,021 1/1956 Taft l15-34 X 2,769,611 11/ 1956Schwarzkopf. 3,167,361 1/1965 Snapp et al. --34 X 3,209,720 10/ 1965Campbell et al. 3,231,022 1/1966 Schroeter et a1. 160.6 3,324,953 6/1967 Greenhill 170160.6

FOREIGN PATENTS 11,822 1889 Great Britain.

TRYGVE M. BLIX, Primary Examiner US. Cl. X.R. 308-239

